Snap action latch



' Dc. 24, 1963 E. P. BUGGE SNAP ACTION LATCH Filed Jan. so, 1961 o "4 31 `-ll ,w M M f ll V5 m p, j w v Q a E 4 2 9 0 32 2 2 3 3 2... v

United States Patent O 3,115,358 SNAP ACTION LATCH I Eiling l. Bugge, P.(). Box 36183, Wlshire-LaBrea Station, i Los Angeles, Calif. Filed Jan. 30, 1961, Ser. No. 85,578

2 Claims. (Cl. 292-78) The present invention relates generally to door latches and more particularly to a spring-loaded, snap-action latch.

A wide variety of spring-loaded locks, catches and latches for doors are commercially available. Customarily, these devices employ helical compression or tension springs or, sometimes, varieties of leaf springs to .bias a latch member into a locking position. In these prior devices, when the latch is in latching position, the spring is in a semi-relaxed condition. However, this arrangement partially defeats the purpose of the spring because'the spring then exerts the least restraining force while the latch member is in the latching position. Then, when the door is opened the latch member, during the course of over-riding the strike, subjects the spring to a gradually increasing load and the spring reacts, of course, by gradually increasing the resistance to the opening movement. a

In my invention, a cabinet latch or the like is given a snap action by a spring means that is adapted to exert its greatest resistance to opening movement of the door, or at the moment of initial contact of the latch with a strike means during opening and closing. With this arrangement, the spring means exerts its greatest force to retain the door snugly closed and reduces its resistance during opening of the door. Conversely, during closing, after the initial impact of the latching member with the strike or catch means, the spring means offers decreased resistance to the closing movement whereby to make closing easier and positive in action.

Another object of the invention is to provide a snapaction latch of simplied construction, involving a minimum number of parts that can very readily be fabricated, assembled and mounted in place. The invention thus provides a superior snap-action latch at a low cost.

These and other objects and advantages of my invention will be apparent from the following description of a presently preferred embodiment thereof, when taken in conjunction with the annexed drawings wherein:

FIGURE 1 is a perspective view of the presently preferred embodiment of my invention, holding a door in the closed position;

FIGURE 2 is a vertical sectional view of the latch assembly shown in FIGURE 1, taken substantially along the median plane of the latch housing;

FIGURE 3 is a view similar to FIGURE 2, but showing the relationship of the parts of the latch assembly at the moment of least resistance of the spring means;

FiGURE 4 is a horizontal sectional view taken on the line 4 4 of FIGURE 2; and

FIGURE 5 is an exploded perspective view of the parts of the latch assembly.

Referring to FIGURE l, the complete device includes a latch assembly mounted on a door and a strike assembly mounted on a shelf 11. However, it will be appreciated that tlie positions of the latch assembly and strike assembly can be reversed and, also, that the hardware is not limited to the mounting of the strike assembly on a horizontal surface. The latch assembly comprises a housing 12, a latch member 13, a spring 14 and a cover plate 15. The strike assembly comprises a bracket 16, a roller 17 and a shaft 13 for mounting the roller on the bracket.

The housing 12 is preferably drawn from a single blank Fice of sheet metal into a shallow, substantially rectangular, box-like conguration, having opposite end walls 19, opposite side walls 20 and a front wall 21. A pair of external tabs 22 are formed integrally with the side walls 20 of the housing and each of these tabs is formed with a slot 23 running parallel to the longitudinal dimension of the housing 12. These slots are adapted to receive wood screws 24, or other suitable fasteners, for securing the latch assembly to the inner face of the door 10. As is apparent, the slots 23 permit adjustment of the latching assembly relative to the strike assembly, thus facilitating installation of the complete device.

The latch member 13 is also preferably made of a single blank of sheet metal that is bent to the coniiguration shown in FIGURE 5. At its rear end, the latch member has a flange 25 disposed normally to the body of the latch member 13 and having a width matingly complementary to the length of a transversely extending slot 26 formed in the front wall 21 of the housing 12. At the junction of the flange 25 with the body of the latch member 13, a pair of shoulders 27 are formed in the latch member for abutment with the exterior surface of the front wall 21 of the housing 12. As is apparent, during assembly the flange 25 is inserted through the slot 26 of the housing and the engagement of the shoulders 27 with the front wall 21 provides pivotal movement of the latch member 13 on the housing 12.

The cover plate 15 closes the open side of the housing 12 and also serves as the support for the spring 14. This cover plate is generally rectangular in conguration and along its longitudinally extending sides has integrally formed flanges 2S which are receivable inside of the opposite side walls 2t) of the housing 12 and serve to ndex the cover plate in the housing. At its opposite ends, the cover plate 15 has a pair of oppositely inclined tabs 29 that are receivable inside of the opposite end walls 19 of the housing 12.

The spring 114 is preferably made of a substantially rectangular sheet of spring steel and, in FIGURES 2 and 5, is shown in its relaxed state. The spring 14 has a width which is freely receivable between the flanges 28 of the cover plate 15, but has a length exceeding the space between the tabs 29 of the cover plate. In the relaxed state, the spring 1'4 has a concave-convex transverse crossseotional iconguration and the spring is assembled to present its concave face to the cover plate 15, the concave face having bearing contact only with the ends of the ltabs 29.

lIn assembling the latch, the latch member flange 25 is first inserted into the slot 26 of the housing 12 and the latch member then pivoted until the ange abuts the inner surface of the front wall 21. The spring 14 and cover plate 15 are then superimposed on the flange 25, care being taken to insure that the opposite longitudinal edges of the spring 14 are received between the flanges 28 of the cover plate. The opposite end walls 1'9 of the housing i12 `are formed with a pair of small ears 30, which are iinally bent over the opposite ends of the cover plate y15 to hold the assembly together. l

The web portion of the bracket `16 is formed with a longitudinally extending slot 31 to receive another wood screw 24 for securing the bracket in the proper position on the shelf 111, relative to the latch assembly on the door .10. The forward or swingable end of the latch member 13 is reversely bent to form a forwardly facing cam 32 and -a rearwardly facing catch 33. The catch portion 33 is preferably normal to the plane of the body of the latch member 13 and, -when the latch is closed, has tangential contact with one side of the roller 17 of the strike assembly. The cam portion 32 defines a forwardly pointing acute angle with the body portion of the latch member 13 and has initial contact with the other side of the roller 17 during closing of the latch.

'The latch is shown in the closed position in FIGURE 2, in which condition spring 14 is in a substantially relaxed state. It will be observed that the space between the convex surface of the spring I14 and the inner surface of the front wall 21 of the housing 12 is such as to snugly accommodate the thickness of the latch member iiange 25, without any appreciable play. When an opening p-ull is exerted on the door `10, the latch member 13 pivots on the shoulders 27, because of the camming engagement of the catch portion 33 with ythe roller 17. The latch member 13 is shown in its position of maximum deiiection in FIGURE 3, rwhich is also the moment of maximum deection of the spring d4 by the end of the ange 25. Because of the configuration of the spring 14, when it is in the condition of maximum deflection shown in FiG- URE 3, it exerts the least resistance to the opening movement and, conversely, to the closing movement.

As is shown in iFIGURE 2, the end of the lflange 2S terminates in t-he mid-portion of the length of the spring 14, i.e., approximately midway between the supporting tabs. 29. Referring to FIGURE 4, lit will be seen that this edge of the flange 25 has substantially tangential contact with the convex face of the spring 14 and ample deflection clearance space is provided between the concave face of the spring and the cover plate 15.

Due to its configuration and its height-thickness ratio, the spring 14 is semi-rigid in the unstressed condition, Thus, when the door is closed, as in FIGURE 2, the ange 2S is firmly held by `the substantially undeflected spring against the inner surface of the front wall 21 of the housing 12, and the catch portion 3-3 of the latch member is lfirmly locked against one side of the roller 17.

Now, wheny an opening pull is initiated on the door 10, the latch member 13 tends to pivot about the shoulders 2.7 to move the edge of the -flange 25 in clockwise direction -against the convex face of the spring 14. The spring 14` acts. very much like a Belleville washer and requires a greater application of force to cause initialdee'ction of the spring than -is required to carry through the deflection of the spring to the maximum indicated in FIGURE 3. Accordingly, the door 10 can oniy be opened by a deliberate forceful pull applied thereto and not by any inadvertently applied lesser force.

Once sufiicient force has been applied to the spring 14 to initiate its buckling by the edge of the lflange 2S, only diminished force is required to carry out the full deflection of the spring, and pivotal movement of the latch member 13, to the ycondition shown in FIGURE 3, which condition is the moment of least resistance offered by the spring .14. When outward movement of the doo-r y10 is continued beyond the position shown in FIGURE v3, the latch member 1-3 is. snapped back into the normal or latching position by the spring 14.

Assuming the door now to be fully open, when it is moved inwardly towards the shelf L1 the cam portion 32 of the latch member has initial tangential contact with the surface of the roller 17 along a trace of the roller positioned above the axis` of the supporting shaft 1'8. Just as in opening the door 10, so, too in closing, a greater force must be applied to the spring 114 in order to initiate buckling than is required to `continue closing the door. Thus, in FIGURE 3, if the door 10 is assumed to be closing, the spring 14 is in a condition of least resistance to the closing movement. Upon continuing the closing movement of the door 10 beyond the position shown in FIGURE 3, as the downwardly pointing apex defined by the cam portion 32 and the catch portion 33 of the latch member passes over center of the roller supporting shaft 1S, the spring 14 and latch 13 will snap back to the condition shown in FIGURE 2.

lit will be understood that the invention is not limited to the details of construction set rforth above since various changes will occur to those skilled in the art, which may be made in the construction, arrangement and proportions of the parts without departing from the scope of the invention as set forth in the following claims.

I claim:

l. A latch assembly comprising: a shallow housing; a latch formed with a flange on one end, said flange being received through a complementary slot Iformed in a front wall of said housing, said latch having pivotal bearing engagement with said front wall of s-aid housing; a cover plate mounted on said housing in rearwardly spaced parallel relationship' to said front wall; a plate spring, normally of concave-convex crocs-sectional configuration, supported within said housing in parallel spaced relationship to said front wall and to said cover plate, said ange of said latch being engaged by the convex face of said spring plate to normally hold said flange in 'contact with the inner sunface of said front wall of said housing in the latching position of said latch.

2. A latch assembly comprising: a shallow substantially rectangular housing that ope-ns rearwardly; a latch fio-uned with a flange on one end, said flange being received through a complementary slot formed in a front wall of said housing, said latch having a pair of opposite rearwardly facing sihouiders positioned forwardly of said flange and pivotally abutting the exterior of said front wall of said housing for movement of lsaid latch between latching and releasing positions; a substantially rectangular cover plate mounted on said housing in rearwardly spaced parallel yrelationship to said front wall and having a pair of integrally formed tabs at opposite ends of said cover plate along the longitudinal center line of said cover plate and extending inwardly of said housing; a substantially rectangular plate spring of concave-convex transverse cross-sectional configuration within said housing and having a length exceeding the spacing between the ends of said pair of tabs of said cover plate, said tabs providing bearing support for opposite ends of the concave face of said spring plate and holding a central area of the convex face of said spring plate in contact with said iange of said latch member, said spring plate in undeflected condition having its convex face holding said flange against the inner surface of said front walll of said housing in the latching position of said latch, the end of said flange being positioned at substantially the midp'ortion of said spring plate ifor buckling said spring plate upon releasing movement of said latch, said spring plate being adapted Ito offer lgreater resistance to deection when said latch is in latching position than when said latch is in releasing position.

References Cited in the file of this patent UNITED STATES PATENTS 2,175,348 Hagstrom Oct. l0, "1939 2,987,337 Fischer June 6, 1961 FOREIGN PATENTS 65,6122 Denmark Aug. 25, l1947 

1. A LATCH ASSEMBLY COMPRISING: A SHALLOW HOUSING; A LATCH FORMED WITH A FLANGE ON ONE END, SAID FLANGE BEING RECEIVED THROUGH A COMPLEMENTARY SLOT FORMED IN A FRONT WALL OF SAID HOUSING, SAID LATCH HAVING PIVOTAL BEARING ENGAGEMENT WITH SAID FRONT WALL OF SAID HOUSING; A COVER PLATE MOUNTED ON SAID HOUSING IN REARWARDLY SPACED PARALLEL RELATIONSHIP TO SAID FRONT WALL; A PLATE SPRING, NORMALLY OF CONCAVE-CONVEX CROSS-SECTIONAL CONFIGURATION, SUPPORTED WITHIN SAID HOUSING IN PARALLEL SPACED RELATIONSHIP TO SAID FRONT WALL AND TO SAID COVER PLATE, SAID FLANGE OF SAID LATCH BEING ENGAGED BY THE CONVEX FACE OF SAID SPRING PLATE TO NORMALLY HOLD SAID FLANGE IN CONTACT WITH THE INNER SURFACE OF SAID FRONT WALL OF SAID HOUSING IN THE LATCHING POSITION OF SAID LATCH. 